Building Second Story Additions

I received the following question in an email and I thought the answer might be useful to others, so rather than just respond in email, I’ve posted it here .

I’ve spoken to many hundreds of excited owners over the years who want to add a second floor on the house and Natalie asked the typical questions.

Question:

We need to add on to our house at least one bedroom, and a guest room would be nice as well. The way our house is situated, the most aesthetically pleasing way to do it would be to add a couple of rooms on a second floor.

My question to you is, what are the limitations with adding on a second story to a house that is currently only a single story? Can it be done, or will it be prohibitively expensive. Any experience you have to share would be appreciated! – Natalie

Answer:

Hi Natalie,

I appreciate your question and I do have some experience I can share. My company has designed and built a few dozen second floor additions over the years.

Let me break down your question into segments.

Can it be done?

Yes. There is no such thing as a house that cannot receive a second floor addition one way or another; or at least not one I’ve seen yet…somebody will probably send me a picture of a house under a concrete overpass or something.

Years ago, after struggling with engineer after engineer on job after job trying to determine if the existing first floor foundation would hold up a second floor, I decided to skip the first floor footings altogether.

The truth is that most newer one story homes have almost zero “extra” strength built into them. As such, most one-story homes have insufficient foundations for the added loads of a two-story. Each state has it’s own set of building codes and Florida is among the most stringent, so a local professional will be able to help you better in that particular area. The lengths I’m accustomed to going to might not be required everywhere.

In the event that the existing foundation is insufficient, there are two options. First, you can augment the existing foundation with additional concrete and steel. The other option, the one I went to on all second story additions, is to build new footings for the second floor itself.

We did this by essentially building a “stilt house” within the existing home. Structurally speaking, these were like two independent structures. You could remove the first floor from under the addition, and it would remain intact.

This is done by placing adequate foundations directly under posts (we often used 6×6 posts) which supported the framing for the second floor. I would design the additions so that these posts can be placed inside existing or new first floor walls, or otherwise integrated into the first floor design with new features. The point being that these posts are “invisible” after the work is done.

So, this is a very long way of explaining that yes, it can be done in almost any house.

Is it prohibitively expensive?

Second floor additions are more costly than first floor additions, but I wouldn’t say prohibitively so. In my experience, the cost for a second floor job is about 20%-30% more than the same square footage built on the ground level. The majority of this extra cost has to do with the requisite remodel of the area under the addition and the cost of the stairs and stairwell.

The cost of an addition can be quite a bargain in times like this when the money you might effectively “lose” by selling in a depressed market is substantial. If you feel an addition of any type would be a good investment, I wouldn’t let the cost of a second floor addition scare you off.

Other Considerations:

Design

A good design is always an absolute imperative on a room addition. I would advise you to not compromise on this. Work until you have a design that meets your needs and you feel will be aesthetically pleasing.

Second floor design work is much more challenging, so you want to be certain that you’re working with someone who has experience in second story additions. If someone says “I haven’t really done many, but it’s no big deal.”, don’t believe them. It is a big deal and the design is the key.

Living During Construction

First floor additions have the great advantage of being able to be completed to a 95% level before breaking into your living space. Even if you’re remodeling adjacent space, the construction area can be effectively sealed off from your home.

Not so with a second floor addition. If the area where you plan to add-on is over an important living area, it could present a real problem. You really need to be able to move-out of the area directly under the addition for the duration of the project.

I’ve had a few clients move to a rental during construction and for a major project that can be a good idea. For most folks, it’s not an option. So plan on “camping-out” in your own home for awhile and be ready for some major inconvenience.

Over the Garage

For a number of reasons, building a second floor over the garage is a great move. The garage has a pretty impressive list of advantages:

The cost to fix-it after construction is much lower since there is no floor covering, basic walls, little trim if any, etc.

The ability of most families to live without the garage for a couple of months is much greater, as compared to the kitchen for example.

The garage floor is often lower than the adjacent house. This is a huge advantage if the skies open and the rain pours down right after they tear the roof trusses off your house. The water will run out of the garage and down the driveway, instead of into your living room.

Hi Tim,
What about settling? I want to build on ‘stilts’ but was reading somewhere that if I build up on anything but the original foundation strengthened, settling can create major issues over time and cracking and damage to stairs and plumbing may result.

Please can you tell me if you have had an long term experiences of this issue? How and can one at all prevent this?

I should go back and review the post above and see if it needs clarification. The support foundations for the “stilt” structure are not independent from the home foundation that already exists. They are integrated the same as an augmented foundation would be using steel and epoxy to connect them, essentially making them one foundation. If designed properly, this should result in a situation where the entire structure is unified and settlement, if any, would be together.

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